Fe2O3-Mediated photocurrent modulation effect for enhanced selective detection in organic photodiodes

Abstract

Organic photodetectors have made great progress because they offer excellent sensitivity and narrow response through molecular structure control. This study investigates uniform Fe₂O₃ layers formed by atomic layer deposition for use in organic photodiodes, focusing on their role in photocurrent amplification under reverse bias conditions. Fe₂O₃, a semiconducting oxide with an indirect band gap, was fabricated at various thicknesses to minimize high charge recombination. Since the lifetime of photogenerated charge carriers from Fe₂O₃ under green light illumination is short, they recombine with charge carriers in the active layer, providing light selectivity. This effect originates from bidirectional charge transport in both the active layer and Fe₂O₃. J–V characteristics revealed that diodes with a 3 nm Fe₂O₃ layer significantly reduce dark current and exhibit a modulation behavior, unlike the photodiode behavior exhibited by diodes with thicker Fe₂O₃ layers. At the ITO/Fe₂O₃ interface, the built-in potential prevents photocurrent flow until a threshold voltage is reached. Compared with the broad photosensitivity of PEDOT:PSS-based devices, detectivity in blue and infrared regions is improved owing to the generation of selective photocurrents and reduced dark current. This study suggests an efficient pathway for photocurrent modulation of diodes with existing active layers by introducing Fe₂O₃.